理工类C级 阅读理解

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1、理工类C级阅读理解　　第九篇AnEssentialScientificProcess　　Alllifeontheearthdependsupongreenplants.Usingsunlight,theplantsproducetheirownfood.Thenanimalsfeedupontheplants.Theytakeinthenutrientstheplantshavemadeandstored.Butthat’snotall.Sunlightalsohelpsaplantproduceo

2、xygen.Someoftheoxygenisusedbytheplant,butaplantusuallyproducesmoreoxygenthanituses.Theexcessoxygenisnecessaryforanimalsandotherorganismstolive.　　Theprocessofchanginglightintofoodandoxygeniscalledphotosynthesis.Besideslightenergyfromthesun,plantsalsouse

3、waterandcarbondioxide.Thewatergetstotheplantthroughitsroots.Thecarbondioxideenterstheleavesthroughtinyopeningscalledstomata.Thecarbondioxidetravelstochloroplasts,specialcellsinthebodiesofgreenplants.Thisiswherephotosynthesistakesplace.Chloroplastsconta

4、inthechlorophyllsthatgiveplantstheirgreencolor.Thechlorophyllsarethemoleculesthattraplightenergy.Thetrappedlightenergychangeswaterandcarbondioxidetoproduceoxygenandasimplesugarcalledglucose.　　Carbondioxideandoxygenmoveintoandoutofthestomata.Watervapora

5、lsomovesoutofthestomata.Morethan90percentofwateraplanttakesinthroughitsrootsescapesthroughthestomata.Duringthedaytime,thestomataofmostplantsareopen.Thisallowscarbondioxidetoentertheleavesforphotosynthesis.Asnightfalls,carbondioxideisnotneeded.Thestomat

6、aofmostplantsclose.Waterlossstops.　　Ifphotosynthesisceased,therewouldbelittlefoodorotherorganicmatterontheearth.Mostorganismswoulddisappear.Theearth’satmospherewouldnolongercontainoxygen.Photosynthesisisessentialforlifeonourplanet.　　词汇：　　nutrientn.营养物　

7、　organismn.生物体，有机体　　carbondioxiden.二氧化碳　　chloroplastn.叶绿体　　moleculen.分子　　vaporn.水蒸气　　oxygenn.氧气　　photosynthesisn.光合作用　　chlorophylln.叶绿素　　glucosen.葡萄糖　　ceasev.停止　　注释：　　1.Thenanimalsfeedupontheplants.动物以植物为食。　　练习：　　1.Inthefirstparagraph，theword“excess”me

8、ans　　A　heavy.　　B　extra.　　C　green.　　D　liquid.　　2.Whichofthefollowingdoesnotmovethroughaplant’sstomata?　　A　Carbondioxide.　　B　Watervapor.　　C　Oxygen.　　D　Food.　　3.Inthetitle,thetermEssentialScientificProcessrefersto　　A　photosynthesis.　　B　the